JP3502841B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a transfer / separation section structure for reliably transferring a toner image onto a transfer sheet. In particular, the present invention relates to an image forming apparatus that has a sheet feeding unit that accommodates a sheet by arranging an image forming unit including a photosensitive drum in the uppermost stage of roll paper feeding and that is provided in a lower stage with respect to the apparatus body.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus, a toner image formed by a toner image forming apparatus composed of a photoconductor or the like is transferred at a transfer unit to a transfer paper carried from a paper storage unit to the surface of the photoconductor, and a separation unit. Then, the transfer paper is separated from the photoconductor, and the toner image is fixed at the fixing portion and then discharged. FIG. 7 is a configuration diagram around a photoconductor of a conventional image forming apparatus. FIG. 8 is a plan view of the transfer / separation charger shown in FIG. 7 viewed from the photoconductor side, and shows only the left half portion thereof. Photoconductor 1
0 is positively charged by the charging unit 11, and the transfer region of the photoconductor 10 is exposed by the exposure unit 9 to form an electrostatic latent image. Next, the negatively charged toner supplied from the developing unit 12 to the photoconductor 10 adheres to the electrostatic latent image to perform development, and the charge eliminating lamp 13 erases electric charges in unnecessary areas on the photoconductor 10. To be done. On the other hand, the transfer sheet conveyed along the conveyance path formed by the conveyance guides 106 and 107 by a pair of registration rollers (not shown) in synchronism with the development is guided by the conveyance guides 104 and 105, and the pre-transfer roller pair. It is carried into the surface of the photoconductor 10 by 103. And
The toner image is transferred onto the transfer paper by the transfer unit 14 which is positively charged, and the transfer paper is separated from the photoconductor 10 by the separation unit 15 including an AC power source and sent to the fixing unit (not shown) along the conveyance guide 27. .

The transfer separation charger 31 includes a charge wire 3
4, 35, a shield case 33, etc.
And the separation part 15 are integrally configured. The minute-diameter charge wires 34, 35 are stretched on both sides of a metallic partition plate 36 with both ends insulated from the shield case 33. The charge wire 34 is connected to a positive DC high-voltage power source (not shown) to configure the transfer unit 14, and the charge wire 35 is connected to an AC high-voltage power source (not shown) to configure the separation unit 15, each of which has a high voltage. Is applied, corona discharge occurs. The metal shield case 33 has an opening surface on the side of the photoconductor 10 and shields the charge wires 34 and 35 from other directions so that corona discharge occurs only in the photoconductor 10 direction. Further, as shown in FIG. 8, nylon threads 37 are stretched over the opening surface side of the shield case 33 at a required interval. As a result, the transferred transfer paper is prevented from entering the shield case 33 without disturbing the corona discharge generated in the direction of the photoconductor 10.

Conventionally, in the transfer / separation charger 31, a line connecting the upper ends of the wall surfaces 38 and 39 of the shield case 33, that is, a nylon thread 37 stretched on the opening surface connects the center of the photoreceptor 10 and the charge wire 34. Are arranged so as to be substantially parallel to the tangential direction with respect to the peripheral surface of the photoconductor 10 at the intersection of the and the peripheral surface of the photoconductor 10. Further, conventionally, a roll paper is stored in a paper storage unit and cut into a predetermined size to be used as a transfer paper. In this case,
As schematically shown in FIG.
It is arranged so as to curl in a direction away from the photoconductor 10 when being conveyed along. This prevents the transfer paper from being wrapped around the photoconductor 10.

[0005]

However, the image forming apparatus using the roll paper arranged as described above, or the image forming unit including the photosensitive drum is arranged at the uppermost stage to accommodate the paper and to the apparatus main body. In the image forming apparatus having the paper storage unit provided in the lower stage, since the transfer paper is curled in the direction away from the photoconductor 10, the leading end portion of the transfer paper is hard to come into close contact with the photoconductor 10. There was an area that could not be transferred. Further, as shown in FIG. 9, when the corner portion of the leading end of the transfer paper P passes through the middle of the nylon thread 37 stretched over the opening surface of the transfer separation charger 31, the transfer paper is curled downward, so that the corner is formed. The portion of the toner enters the inside of the case through the gap of the nylon thread 37 and contacts the wall surface 39 of the shield case 33 on the side of the separating portion 15, and the corner portion is repelled as the transfer sheet is conveyed, and the toner image transferred onto the transfer sheet is generated. There was a risk that the problem of scattering would occur.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an image forming apparatus capable of transferring a toner image to the front end portion of a transfer paper. Further, the present invention is
An object of the present invention is to provide an image forming apparatus in which a corner portion at the tip of a transfer sheet does not come into contact with a downstream side wall surface of a transfer separation charger.

[0007]

[Means for Solving the Problems] A paper accommodating portion in which roll paper is set, a cutting device for cutting the conveyed roll paper into a transfer paper of a predetermined size, respectively, from the upstream side of a transfer paper conveyance path. An image forming apparatus having at least an image forming system including a photoconductor, and a transfer separation charger having a transfer charger having an opening on the side of the photoconductor and a separation charger arranged in parallel in the rotation direction of the photoconductor. The shape of the charger is
A box-shaped shield case, and the height dimension of the downstream wall surface on the downstream side in the photoconductor rotation direction is larger than the height dimension of the upstream wall surface on the upstream side in the photoconductor rotation direction of the shield case, A plurality of thread-like members stretched in a line in a direction extending outward from the widthwise center of the shield case with respect to the rotation direction from the upper end of the upstream wall surface to the upper end of the downstream wall surface of the opening surface of An image forming apparatus characterized in that It is provided (Claim 1).

Further, in the thread member, at least the distance between the thread member immediately inside the point where the widthwise end of the transfer paper passes through the downstream wall surface and the thread member immediately outside of the point are greater than the distance between the other portions. The image forming apparatus according to claim 1, wherein the image forming apparatus is stretched so as to become narrower (claim 2).

A point where the widthwise end of the transfer paper intersects the downstream wall surface is defined as a first point, and a point at which the thread member supports the widthwise end portion at a position closest to the downstream wall surface is a first point. 3. The image forming according to claim 2, wherein the thread member is stretched so that the dimension between the first point and the second point is equal to or less than a predetermined value. An apparatus is provided (Claim 3).

A point where the widthwise end of the transfer paper intersects with the downstream wall surface is defined as a first point, and a point at which the thread member supports the widthwise end portion at a position closest to the downstream wall surface is referred to as a first point. Assuming that the second point is a point at which the thread member immediately inside the thread member supporting the second point is stretched on the downstream wall surface, the third point is that the thread member is the first point. The image forming apparatus according to claim 2, wherein the image forming apparatus is stretched so that the dimension between the third points is equal to or less than a predetermined value.

A point where the widthwise end of the transfer paper intersects the downstream wall surface is defined as a first point, and a point at which the thread member supports the widthwise end portion at a position closest to the downstream wall surface is a first point. Assuming that the second point is a point at which the thread member immediately inside the thread member supporting the second point is stretched on the downstream wall surface, the third point is that the thread member is the first point. The image according to claim 2, wherein the image is stretched so that the sum of the dimension between the second points and the dimension between the first point and the third point is equal to or less than a predetermined value. A forming apparatus is provided (Claim 5).

[0012]

According to the first aspect of the invention, the roll paper is used in the paper storage section. Roll paper has a particularly large curl compared to plain paper because it is originally wound. Therefore, in the present invention, since the curl is larger than the height dimension of the upstream wall surface of the shield case on the upstream side in the rotation direction of the photoconductor, the transfer carried between the photoconductor and the transfer charger is performed. Since the leading edge of the paper is conveyed closer to the photoconductor, the toner image is reliably transferred to the leading edge of the transfer paper. Further, since the thread-like member is provided on the opening surface of the shield case, the transfer paper can be prevented from entering the shield case from the opening surface.

Further, according to the second aspect of the invention, the widthwise end portion of the front end of the transfer sheet to be conveyed, that is, the corner portion of the transfer sheet is securely supported by the thread member, and the upper end of the downstream wall surface of the shield case. It is transported without contact with.

According to the third aspect of the invention, the widthwise end portion of the transfer sheet to be conveyed is supported by the thread member at a position closer to the downstream wall surface of the shield case, and the downstream wall surface of the shield case is supported. It is transported without touching the upper end.

According to the fourth aspect of the invention, on the downstream wall surface of the shield case, the front end of the transferred transfer paper is supported by the thread member at a position closer to the widthwise end, that is, the corner of the transfer paper front end. Thus, the shield case is conveyed without coming into contact with the upper end of the downstream wall surface of the shield case.

According to the fifth aspect of the invention, the widthwise end of the conveyed transfer paper, that is, the corner of the transfer paper is supported by the filamentous member at a position closer to the downstream wall surface of the shield case. And is conveyed without contacting the upper end of the downstream wall surface of the shield case.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus to which the present invention is applied will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration around a photoconductor of the same embodiment, and FIG. 6 is a diagram showing a schematic configuration including a transfer paper transport system in addition to the photoconductor periphery. This image forming apparatus is internally provided with various components such as an image forming system and a transfer paper conveying system.

The image forming system is composed of a photoconductor 10 on which an electrostatic latent image is formed, and respective portions arranged around the photoconductor 10. Around the photoconductor 10, a charging unit 11 that charges the photoconductor 10 to a predetermined positive potential, an exposure unit 9 that exposes a transfer area of the photoconductor 10 to form an electrostatic latent image, and a toner that is negatively charged. A developing unit 12 for adhering to an electrostatic latent image for development, a charge eliminating lamp 13 for erasing electric charges in unnecessary areas on the photoconductor 10, and a transfer unit 1 for transferring a toner image onto a transfer sheet.
4. A separation unit 15 for separating the transfer paper from the photoconductor 10 and a cleaning unit 16 for cleaning the toner remaining on the surface of the photoconductor 10 after the transfer are arranged. Transfer part 1
4 and the separation unit 15 are integrally configured as a transfer separation charger 31 as described later.

Further, the transfer paper transport system is provided with a wide roll paper 17 capable of printing, for example, A1 portrait or A2 landscape size and an A0 portrait or A1 landscape size in order from the upstream side in the transport direction. A paper storage unit in which a wide roll paper 18 is set, a pair of paper feed rollers 19 and 2 for feeding each roll paper
0, a pair of transport rollers 21 for transporting roll paper, a cutter 22 for cutting the transported roll paper into transfer paper of a predetermined size,
Registration roller pair 2 that conveys the transfer paper in synchronization with development
3, a pre-transfer roller pair 24 that conveys the transfer paper toward the photoconductor 10, and conveyance guides 25 and 26 that guide the transfer paper to the photoconductor 10. Further, a conveyance guide 27 for guiding the transfer sheet to a fixing unit (not shown) is arranged downstream of the transfer sheet after the transfer in the conveying direction. The film 8 arranged immediately upstream of the pre-transfer roller pair 24 presses the transfer paper against the roller surface to prevent waviness and bending.

Next, the structure of the transfer / separation charger 31 having the transfer section 14 and the separation section 15 will be described with reference to FIGS. The transfer / separation charger 31 is used for the transfer paper photoreceptor 10.
The charge wires 34 and 35, the shield case 33, and the like are arranged immediately downstream of the carry-in position in the rotational direction of the photoconductor 10.

FIG. 2 is a plan view of the transfer / separation charger 31 as seen from the photosensitive member 10. For convenience of explanation, the left half portion thereof (see FIG. 1).
Only the inside, the front side) is shown, and the cover of the attachment portion of the charge wires 34, 35 is shown broken. Figure 3 (a) shows
FIG. 3B is a partially enlarged view of FIG.
FIG. 5 is a view taken in the direction of arrow B in FIG. Figure 4
2 is a view taken in the direction of arrow A in FIG. 2, and the attachment portions of the charge wires 34 and 35 are not shown.

The minute-diameter charge wires 34 and 35 are made of, for example, tungsten, and one end thereof is shown in FIGS.
As illustrated in FIG.
3 and 44, the other end is fixed with a screw (not shown) via a similar support member (not shown) in a state of being insulated from the shield case 33, and stretched in parallel with each other by the elastic force of the coil springs 43 and 44. It is hung. Also, the charge wire 34
Has one end connected to a positive DC high-voltage power source (not shown) of several kV through a wiring cable, a banana plug, or the like to form the transfer portion 14, and the charge wire 35 has one end through a similar member. Is connected to an alternating-current high-voltage power supply (not shown) to form a separating portion 15, and a corona discharge is generated when a high voltage is applied to each of them.

The shield case 33 has an opening on the side of the photoconductor 10 and shields the charge wires 34 and 35 from the other direction so that corona discharge occurs only in the direction of the photoconductor 10. The shield case 33 is made of a conductive material such as aluminum, iron or stainless steel as shown in FIG.
The wire portion 32 and the case portion 53 are formed of an L-shaped member 51 and a U-shaped member 52 molded into a predetermined shape as shown in FIGS.

The wire portion 32 is constructed by spot-welding an L-shaped member 51 on a U-shaped member 52. U-shaped member 5
2 is a charge wire 34 at the mounting portion at both ends in the width direction,
35 is fixed as described above, and the bending strength is increased by the U-shape. The L-shaped member 51 is a U-shaped member 52.
A shorter size charge wire 34 at both ends of the U-shaped member 52,
The vertical portion 51 a is disposed between the mounting portions 35 and forms a boundary between the transfer portion 14 and the separation portion 15.

The case portion 53 is on the transfer portion 14 side (photoreceptor 1).
0, the wall surface 531 on the upstream side in the rotation direction), the wall surface 532 and the bottom surface 533 on the separation unit 15 side (the downstream side on the rotation direction of the photoreceptor 10).
And the like are formed in a box shape. Wall 531,532
Has an inclined surface 531a, 532a formed in the upper part by being bent in the rotation direction of the photoconductor 10. This slope 5
Reference numerals 31a and 532a guide the transfer paper conveyed between the transfer charger 31 and the photoconductor 10 so as to smoothly pass therethrough.

The case portion 53 is formed such that the height dimension of the wall surface 532 is larger than the height dimension of the wall surface 531. The height dimension is, for example, a straight line L that is parallel to the tangential direction from the intersection of the line connecting the central axes of the charge wire 34 and the photoconductor 10 and the peripheral surface of the photoconductor 10 and that passes through the upper end of the inclined surface 531a. The upper end of the surface 532a and the inclined surface 5
The angle φ formed by the straight line connecting the upper ends of 31a is φ = 3.9 °
Is set to.

Further, the case portion 53 has a thread member 37.
However, they are stretched over the opening surface side at required intervals as described later. The filamentous member 37 is made of nylon, for example, and supports the transfer paper being conveyed, and supports the shield case 3 from the opening surface.
It is intended to prevent the invasion into the inside of 3. The transfer separation charger 31 is configured as shown in FIG. 4 by inserting the wire portion 32 into the case portion 53 from the front side in FIG. As shown in FIG. 3A, the bottom surface 533 of the case portion 53 has a rectangular hole 533a of a required size.
And a rectangular hole 51b of a required size is formed on the bottom surfaces of the U-shaped member 52 and the L-shaped member 51, and ozone having a larger specific gravity than the air generated by the corona discharge of the charge wire 35 is released downward. I am trying. Next, the interval between the thread members 37 stretched over the opening surface of the shield case 33 will be described with reference to FIGS. 2 and 3A.

In FIG. 3A, a point where the widthwise end of the transfer paper P conveyed in the gap between the case portion 53 and the photoconductor 10 passes through the inner surface of the wall surface 532 is P1, and the widthwise end is the most. The point where the thread member 37 is supported at a position close to the wall surface 532 is P2, the intersection point between the thread member 37 stretched inward from the widthwise end and the inner surface of the wall surface 532 is P3, and the point P
The dimension between 1 and P2 is d1, and the dimension between points P1 and P3 is d2
And In FIG. 3A, the point P2 is placed on the thread member 371.
However, the point P3 is located on the thread member 372. Further, in the present embodiment, the tension interval of the thread-like member 37 is as shown in FIG.
A: d1 ≦ 10 at four places in the middle areas Q1 to Q4
mm, B: d2 ≦ 10 mm, C: d1 + d2 ≦ 30 mm
Is set to either. The numerical values on the right side of A to C are determined irrespective of the size of the roll paper set in the paper storage unit. Here, the region Q1 is a region through which the widthwise end of the transfer paper formed by cutting the roll paper 18 passes, and the region Q3 is the widthwise end of the transfer paper formed by cutting the roll paper 17. This is the area through which the section passes.

Further, in regions other than the regions Q1 to Q4 where the widthwise ends of the transfer paper do not pass, the tension intervals of the thread members 37 are slightly wider than the regions Q1 to Q4. It is set to a required interval that can be supported over. With the above configuration, the charging unit 11 charges the photoconductor 10 and the exposure unit 9 exposes the transfer region of the photoconductor 10 to form an electrostatic latent image. Next, the developing unit 12
The negatively charged toner supplied to the photoconductor 10 from the toner adheres to the electrostatic latent image and is developed. On the other hand, roll paper 1
7 or 18 is conveyed by a pair of paper feed rollers 19 or 20, further conveyed by a pair of conveyance rollers 21, and cut into transfer paper of a predetermined size by a cutter 22. Next, the transfer sheet is conveyed by the registration roller pair 23 in synchronism with the development, and is pressed by one of the pre-transfer roller pair 24 across the width of the sheet by the film member 8, and then is sandwiched by the pre-transfer roller pair 24. It is conveyed in the gap between the photoconductor 10 and the transfer separation charger 31.

The front end of the transfer paper is threaded on the opening surface of the case portion 53 of the transfer / separation charger 31.
It is conveyed while abutting against and being supported. At this time, since the upper end of the wall surface 532 on the separation unit 15 side is located closer to the photosensitive member 10 side than the upper end of the wall surface 531 on the transfer unit 14 side with respect to the line parallel to the tangent line of the photosensitive member 10, the leading end portion of the transfer sheet is formed. Are conveyed closer to the photoconductor 10. Further, at the widthwise end portion of the transfer sheet being conveyed, the distance between the thread members 37 is the above,
Narrow area set by either or Q1 or Q3
Since the sheet passes through, the corner portion of the front end of the transfer paper is reliably supported by the filamentous member 37 and is conveyed without contacting the wall surface 532 of the case portion 53. Then, the toner image on the photoconductor 10 is transferred by the transfer unit 14, then separated from the photoconductor 10 by the separation unit 15, and the separated transfer paper is conveyed along the conveyance guide 27, and a fixing unit (not shown). Thus, the toner image is fixed on the transfer paper.

As described above, since the transfer paper is conveyed closer to the photoconductor 10, the toner image can be transferred to the leading end portion of the transfer paper. Further, since the interval between the thread members 37 stretched over the area through which the widthwise end portion of the transfer paper passes is narrowed, the corner portion at the tip of the transfer paper is reliably supported by the thread member 37, and the case portion 53 is formed. It is possible to convey without contacting the wall surface 532.
Therefore, it is possible to prevent problems such as the toner image on the transfer paper being scattered.

In the above-mentioned embodiment, since the areas in which the tension intervals of the thread members 37 are narrowed are provided in four areas Q1 to Q4 in FIG. 2, four types of roll paper are set in the paper storage section. You can choose from different sizes. Also,
By providing an area with a narrow tension interval between the thread members 37 according to the size of the transfer paper set in the paper storage unit, the amount of the thread members 37 to be stretched can be minimized and the tension of the tension can be reduced. Can be reduced. In addition, in the above-mentioned embodiment, although the regions in which the tension intervals of the thread members 37 are narrowed are provided at four places, the thread members 37 are tensioned at the above-mentioned narrow intervals over the width direction of the opening surface of the case portion 53. You may do it. In this case, roll paper of any size can be set in the paper storage unit. Also, the angle φ
Is not limited to 3.9 °. When increasing the angle φ, the numerical values on the right side of the above A to C may be reduced. Further, when the angle φ is reduced, the numerical values on the right side of the above may be increased.

[0033]

As described above, according to the first aspect of the present invention, the paper accommodating portion in which the roll paper is set, the transfer charger having the opening surface on the photoconductor side, and the separation charger are the photoconductors. In an image forming apparatus having at least a transfer separation charger arranged side by side in the rotation direction, the shape of the separation charger is a box-shaped shield case, and the height dimension of the downstream wall surface on the downstream side in the rotation direction is, Since the height of the shield case is larger than the height of the upstream wall surface on the upstream side in the rotation direction of the photoconductor, the end of the transfer paper can be conveyed closer to the photoconductor, especially for the curl peculiar to the roll paper. Therefore,
The toner image can be transferred to the leading end of the curled transfer paper, which is unique to the roll paper. Further, since the thread-like member is provided on the opening surface of the shield case, the transfer paper can be prevented from entering the shield case from the opening surface.

According to the second aspect of the present invention, the filamentous member is provided on the inner side of the filamentous member immediately inside the point where at least the end of the transfer paper in the width direction passes through the downstream wall surface of the shield case of the separation charger and on the outer side immediately outside thereof. Since the thread members are stretched so that the distance between them is narrower than the distance between other parts, it is possible to reliably support and convey the widthwise edge of the transfer paper tip, and It is possible to prevent contact with the upper end of the downstream wall surface of the shield case of the separation charger. Therefore, the toner image transferred on the transfer paper can be surely held.

Further, according to the third aspect of the invention, since the widthwise end portion of the transferred transfer paper is supported at a position closer to the downstream wall surface of the shield case, the corner portion of the transfer paper front end is formed. It is possible to prevent contact with the upper end of the downstream wall surface of the shield case of the separation charger. Therefore, the toner image transferred on the transfer paper can be surely held.

Further, according to the invention of claim 4, on the downstream wall surface of the shield case, the front end of the conveyed transfer paper is supported at the end portion in the width direction, that is, at the position closer to the corner portion of the front end of the transfer paper. Therefore, it is possible to prevent the corner portion at the tip of the transfer paper from coming into contact with the upper end of the downstream wall surface of the shield case of the separation charger. Therefore, the toner image transferred on the transfer paper can be surely held.

Further, according to the invention of claim 5, the widthwise end portion of the front end of the transfer sheet to be conveyed, that is, the corner portion of the transfer sheet is supported at a position closer to the downstream wall surface of the shield case. It is possible to prevent the corner portion of the tip of the transfer paper from coming into contact with the upper end of the downstream wall surface of the shield case of the separation charger. Therefore, the toner image transferred on the transfer paper can be surely held.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration around a photoconductor of an embodiment of an image forming apparatus to which the present invention is applied.

FIG. 2 is a plan view of the transfer / separation charger shown in FIG. 1 as viewed from a photoreceptor.

3A is an enlarged view of FIG. 2, and FIG. 3B is a view taken in the direction of arrow B of FIG. 3A, showing only a part thereof.

FIG. 4 is a view taken in the direction of arrow A in FIG. 2, in which a mounting portion of a charge wire is omitted.

5 (a) and 5 (b) are views showing each member constituting the shield case.

FIG. 6 is a diagram showing a configuration around a transfer paper transport system and a photoconductor of the embodiment.

FIG. 7 is a diagram showing a configuration around a photoconductor of an example of a conventional image forming apparatus.

8 is a plan view of the transfer / separation charger shown in FIG. 7 viewed from a photosensitive member.

FIG. 9 is an enlarged view of FIG. 8 for explaining a conventional problem.

[Explanation of symbols]

10 photoconductor 14 Transfer part 15 Separation part 31 Transfer Separation Charger 33 shield case 34,35 Charge wire 37 Filiform member 53 Case 531,532 wall surface 531a, 532a inclined surface

Continuation of the front page (56) Reference JP-A-8-240995 (JP, A) JP-A 1-2230083 (JP, A) JP-A-58-221873 (JP, A) JP-A-62-245275 (JP , A) JP-A-4-7581 (JP, A) JP-A-5-313514 (JP, A) Actually open 60-44059 (JP, U) Actually open 60-60772 (JP, U) Actually open 4-46457 (JP, U) Actual Kaihei 5-43169 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/14 101 G03G 15/16 102

Claims (5)

(57) [Claims] 1. A paper accommodating portion in which roll paper is set, a cutter for cutting the conveyed roll paper into transfer paper of a predetermined size, and an opening on the photoconductor side in this order from the upstream side of the transfer paper conveyance path. An image forming apparatus including at least a transfer separation charger having a transfer charger having a surface and a separation charger arranged side by side in the rotation direction of the photoconductor, and an image forming system including the photoconductor. Is a box-shaped shield case, and the height dimension of the downstream wall surface on the downstream side in the photoconductor rotation direction is larger than the height dimension of the upstream wall surface on the upstream side in the photoconductor rotation direction of the shield case, A plurality of yarns stretched in a row in the opening surface of the shield case from the upper end of the upstream wall surface to the upper end of the downstream wall surface in a direction extending outward from the widthwise center of the shield case with respect to the rotation direction. An image forming apparatus characterized by comprising a member. 2. In the thread member, at least the distance between the thread member immediately inside the point where the widthwise end of the transfer sheet passes through the downstream wall surface and the thread member immediately outside of the point are greater than the distance between the other portions. The image forming apparatus according to claim 1, wherein the image forming apparatus is stretched so as to become narrower. 3. A first point is a point where a widthwise end of the transfer paper intersects with the downstream wall surface, and a point where the filamentous member supports the widthwise end at a position closest to the downstream wall surface is a first point. 3. The image forming according to claim 2, wherein the thread member is stretched so that the dimension between the first point and the second point is equal to or less than a predetermined value. apparatus. 4. A first point is a point where a widthwise end of the transfer paper intersects with the downstream wall surface, and a first point is a point where the thread member supports the widthwise end portion at a position closest to the downstream wall surface. Assuming that the second point is a point at which the thread member immediately inside the thread member supporting the second point is stretched on the downstream wall surface, the third point is that the thread member is the first point. The image forming apparatus according to claim 2, wherein the image forming apparatus is stretched so that a dimension between the third points is equal to or less than a predetermined value. 5. A first point is a point where a widthwise end of the transfer paper intersects with the downstream wall surface, and a point at which the thread member supports the widthwise end at a position closest to the downstream wall surface. Assuming that the second point is a point at which the thread member immediately inside the thread member supporting the second point is stretched on the downstream wall surface, the third point is that the thread member is the first point. The image according to claim 2, wherein the image is stretched so that the sum of the dimension between the second points and the dimension between the first point and the third point is equal to or less than a predetermined value. Forming equipment.